This invention relates to a utility knife system, which comprises a knife handle, exchangeable blades, and protective covers for the blades.
Utility knives are versatile cutting tools that feature a blade slidable in and out of a knife handle. Typically, to replace the blade of a utility knife when the blade becomes dull, a user must unscrew and open the utility knife handle to gain access to the blade.
To make the replacement of blades more convenient, various configurations for utility knives for which the blades may be replaced without opening the knife handle are known. For example, in U.S. Pat. No. 3,577,637, filed by Braginetz on Sep. 24, 1968 and issued on May 4, 1971, a utility knife is disclosed containing a blade carrier with a resilient portion that can be moved laterally by a tab. The resilient portion contains a lug that engages certain notches on the blade.
As another example, U.S. Pat. No. 3,025,598, filed by Nissen on Oct. 13, 1958 and issued on Mar. 30, 1962, discloses a utility knife having a blade with a rounded, knob-like end. The utility knife handle contains a blade carrier having a resilient upper portion. The upper portion of the blade carrier contains a shoulder. When the blade is inserted into the handle, the rounded end of the blade exerts a downward force on the shoulder, causing the upper portion to depress. When the rounded end passes the shoulder, the upper portion springs back to its normal position, causing the shoulder to engage the rear of the rounded end. To disengage the blade, the upper portion is depressed using a tab coupled to the upper portion.
In each of the above-described known configurations for replacing blades within a utility knife handle, a risk exists that a user may cut himself or herself while replacing a blade because the cutting edge of the blade is left exposed. To date, therefore, each configuration for replacing blades within a utility knife involves a safety risk to the user.